Permissions trong RN — `react-native-permissions` cross-platform pattern?

react-native-permissions là lib chuẩn cho iOS/Android permission.

API thống nhất:

import { check, request, PERMISSIONS, RESULTS } from 'react-native-permissions'

async function requestCamera() {
  const permission = Platform.select({
    ios: PERMISSIONS.IOS.CAMERA,
    android: PERMISSIONS.ANDROID.CAMERA,
  })!

  const status = await check(permission)

  switch (status) {
    case RESULTS.UNAVAILABLE:
      // device không có camera
      break
    case RESULTS.DENIED:
      // chưa được hỏi → request lần đầu
      const result = await request(permission)
      return result === RESULTS.GRANTED
    case RESULTS.GRANTED:
      return true
    case RESULTS.BLOCKED:
      // user từ chối permanent → mở Settings
      Linking.openSettings()
      break
  }
}

Setup config:
- iOS: Info.plist thêm key NSCameraUsageDescription, NSLocationWhenInUseUsageDescription, ... với mô tả lý do (App Store reject nếu thiếu hoặc generic).
- Android: AndroidManifest.xml thêm <uses-permission>. Android 6+ cần runtime request, lib tự handle.

Pattern UX 2026:
1. Pre-prompt: trước khi popup native, hiển thị custom modal explain why → tăng grant rate.
2. Just-in-time request: chỉ request khi feature cần (vd request camera khi user nhấn "Take photo", không request lúc app start).
3. Graceful fallback: nếu denied, app vẫn hoạt động không crash; chỉ hide feature liên quan.
4. Settings deeplink: với BLOCKED, deep link vào Settings app cho user enable manual.

iOS 14+ specific:
- PERMISSIONS.IOS.LOCATION_WHEN_IN_USE vs LOCATION_ALWAYS — request when-in-use trước, sau đó upgrade lên always khi cần background.
- App Tracking Transparency (PERMISSIONS.IOS.APP_TRACKING_TRANSPARENCY) — bắt buộc nếu dùng IDFA.

react-native-permissions is the standard cross-platform permissions library.

Unified API:

import { check, request, PERMISSIONS, RESULTS } from 'react-native-permissions'

async function requestCamera() {
  const permission = Platform.select({
    ios: PERMISSIONS.IOS.CAMERA,
    android: PERMISSIONS.ANDROID.CAMERA,
  })!

  const status = await check(permission)

  switch (status) {
    case RESULTS.UNAVAILABLE:
      // device has no camera
      break
    case RESULTS.DENIED:
      // never asked → request for the first time
      const result = await request(permission)
      return result === RESULTS.GRANTED
    case RESULTS.GRANTED:
      return true
    case RESULTS.BLOCKED:
      // user permanently denied → open Settings
      Linking.openSettings()
      break
  }
}

Config setup:
- iOS: Info.plist adds keys like NSCameraUsageDescription, NSLocationWhenInUseUsageDescription, with a meaningful reason string (App Store rejects missing or generic ones).
- Android: AndroidManifest.xml adds <uses-permission>. Android 6+ requires runtime requests; the library handles it.

2026 UX pattern:
1. Pre-prompt: before the native popup, show a custom modal explaining why → higher grant rate.
2. Just-in-time request: only request when the feature needs it (e.g. ask for camera when the user taps "Take photo", not at app start).
3. Graceful fallback: if denied, the app keeps working without crashing — just hide the related feature.
4. Settings deep link: for BLOCKED, deep-link into Settings so the user can enable manually.

iOS 14+ specifics:
- PERMISSIONS.IOS.LOCATION_WHEN_IN_USE vs LOCATION_ALWAYS — request when-in-use first, upgrade to always when background work demands it.
- App Tracking Transparency (PERMISSIONS.IOS.APP_TRACKING_TRANSPARENCY) — required if using IDFA.